Musical Paradise MP-301 MK3: one channel "broken"

It appears that the left channel of my Musical Paradise MP-301 MK3 is not working any more.
I tried swapping and replacing both pre and amplification tubes, so I can exclude the cause is any tube is damaged.
Any idea of a place in NY where I could bring it for repair?

I have the same exact problem. Everytime I contact them via email I get the runaround.